Mechanism of synergistic photoinactivation utilizing curcumin and lauric arginate ethyl ester against Escherichia coli and Listeria innocua

Authors: Ryu, Victor; Uknalis, Joseph; CORRADINI, MARIA - University Of Guelph; CHUESIANG, PIYANAN - Chulalongkorn University; MCLANDSBOROUGH, LYNNE - University Of Massachusetts, Amherst; Ngo, Helen; Jin, Zhonglin; Fan, Xuetong

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2023
Publication Date: 11/21/2023
Citation: Ryu, V.N., Uknalis, J., Corradini, M.G., Chuesiang, P., McLandsborough, L., Lew, H.N., Jin, Z.T., Fan, X. 2023. Mechanism of synergistic photoinactivation utilizing curcumin and lauric arginate ethyl ester against Escherichia coli and Listeria innocua. Food Chemistry. 12(23). https://doi.org/10.3390/foods12234195.
DOI: https://doi.org/10.3390/foods12234195

Interpretive Summary: Food-grade photosensitizers can increase bacteria inactivation after exposure to light by generating reactive oxygen species which in turn damage bacterial cells. In this study, we investigated how lauroyl arginate ethyl ester (a food preservative) enhanced photoinactivation of bacteria by curcumin (a food-grade photosensitizer). We used several methods to examine changes in morphology, viability, and recovery of Escherichia coli and Listeria. Results showed that lauroyl arginate ethyl ester enhanced the interaction of cell membrane with reactive oxygen species generated by curcumin under ultraviolet A light, leading to significant damages of bacteria which resulted in their inactivation. The information helps develop strategies to further increase photoinactivation efficacy of photosensitizers against human pathogens.

Technical Abstract: This study aimed to investigate the mechanism by which lauroyl arginate ethyl ester (LAE) enhances curcumin photoinactivation. The study used SEM, TEM, Live/Dead cell assays, and monitored changes in solution turbidity, curcumin stability, and bacterial morphology, viability, and recovery. The stock curcumin-LAE solutions were produced by adding curcumin in ethanol to an agitated LAE solution. The photoinactivation of bacteria was achieved by irradiating the curcumin-LAE solution with UV-A light (lambda = 365 nm) containing E. coli and Listeria innocua cocktail. Cell recovery after photoinactivation was monitored by measuring the optical density of bacterial suspensions at pH 3.5 and 7.0 for 24 h using a plate reader, and growth kinetics were characterized using a modified logistic model. The study's findings revealed that the combination of LAE and curcumin inhibited E. coli recovery for 24 hours at pH 3.5, whereas curcumin photoinactivation was more effective at pH 3.5 for L. innocua, and LAE inactivation was more effective at pH 7.0. Cell membrane damage was observed in both E. coli and L. innocua when exposed to LAE and curcumin-LAE solutions using SEM, TEM, and Live/Dead cell assays. However, E. coli remained viable when treated with only curcumin or LAE at pH 3.5, except when both were used under UV-A light. These results suggest that LAE might enhance cell permeability and promote reactive oxygen species (ROS), which are produced by photo-sensitized curcumin, to interact with essential cell components ultimately causing cells to be inactivated.